(kŏp'ər) Symbol CuA reddish-brown, ductile, malleable metallic element that is an excellent conductor of heat and electricity. It is widely used for electrical wires, water pipes, and rust-resistant parts, either in its pure form or in alloys such as brass and bronze. Atomic number 29; atomic weight 63.546; melting point 1,083°C; boiling point 2,595°C; specific gravity 8.96; valence 1, 2. See Periodic Table. See Note at element.